Process of producing amines



Patented Mar. 5, 1935 1,992,935

UNITED STATES PATENT OFFICE PROCESS OF PRODUCING AMINES Herrick R. Arnold, Elmhurst, DeL, assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. ApplicationAugust 2'1, 1930,

. Serial No. 478,317

'15 Claims. (Cl. 260-127) This invention relates to the art of catalysis, supported on silica gel was prepared in the 01- and more particularly to the preparation and lowing manner: 290 grams of a commercial silica use in the catalytic synthesis of amines from gel was evacuated for four hours at 400 C. alcohols and ammonia of porous, rigid gels im- After cooling down invacuo the gel was immersed 5 pregnated with dehydrating oxides. in a solution of 140 grams of aluminum nitrate 5 It is known that certain oxides, such as those in 700 cc. of water. After standing several hours, of thorium, tungsten, and silicon, are capable of the excess liquid was filtered off and the impregcatalyzing various dehydration reactions, includnated gel was dried and ignited at 400 C. to ing the reaction by which amines are prepared decompose the aluminum nitrate contained in from alcohols and ammonia. Certain gels, the pores of the gel. 10 typified by silica gel, have also been proposed as When used in the catalytic synthesis of butyl catalytic material for these reactions, but so far amines by passing butanol and ammonia in mol as I am aware, the improved results to be obratios, varying from 1:3 to 1:6 over 50 cc. of the tained by the use in the synthesis of amines of catalyst at 325 C. with a time oi. contact of gas rigid gels impregnated with dehydrating oxides and vapor of 1.2 seconds, a conversion of the 15 has not thus far been recognized. butanol to mono-, di-, and tri-amines of 5.2%,

This invention has as an object to provide an 16.0% and 4.0% respectively was obtained, the improved process for the catalytic synthesis of total conversion being 25.2%, with a loss to butyaliphatic and aromatic amines. A further object lene of only 0.9%.

is to provide such a process involving the use of Under similar conditions, an unsupported 20 dehydrating oxides supported on a porous, rigid catalyst consisting of aluminum phosphate, gave gel. A specific object is to provide a process for a conversion to amines of 25.3%, the conversion the synthesis of amines involving the use of rigid, to mono-amine being 14.6% and to diand triporous, refractory silica gel impregnated with amines 10.7%, but with a loss to butylene of 8%.

aluminum oxide. Further objects will appear Ewample 2.-A catalyst prepared as described 25 hereinafter. in Example 1 was employed in the synthesis of These objects are accomplished by the followmethyl amine from methanol and ammonia, at ing invention which, in its general aspects, com- 340 C. with a molecular ratio of methanol to prisesthe preparation of a gel in a rigid condi= ammonia of 1.0 and a time of contact of gas and 80 tion and free from absorbed or adsorbed gases vapor with the catalyst of 3.5 seconds. The conor liquids, followed by impregnation with a. soluversion of methanol to methyl amines was 31%,

tion of a salt of the dehydrating metal. After with only 6% conversion to dimethyl ether. filtering, drying, and igniting, the material is Example 3.-As illustrating the rangeof conused in the catalytic synthesis of amines by ditions over which a catalyst prepared in accord- 35 passing a mixture of the desired alcohol and ance with the principles of this invention may be 35 ammonia over the catalyst at an elevated tememployed, the'supported alumina catalyst preperature. In the synthesis of amines from pared as an Example 1 was employed for butyl alcohols and ammonia, it is desirable to use a amine Synthesis at temperatures Varying from catalyst which will produce substantial yields 0 C- o 35 C" with at o am onia to 40 of amines with a minimum conversion to undebutanol varying from 2:1 to 7.521 and time of 40 sirable products, such as the unsaturated hydrocontacting of gas and vapor with the catalyst of carbons. According to the present invention, it about 2.5 seconds. The conversion of butanol to a dehydrating oxide, such as alumina, be deamines at the lower temperature was 20%, posited on the surface of a porous, rigid gel, such losses due to butylene formation constituted only as silica gel, and used as a catalyst for the syn- 0.6%. At the higher temperature the total amine 45 thesis of amines, substantial yields can be obformation was 46% with & blltylehe formation f tained, while the loss due to conversion of alcohol to unsaturated hydrocarbons, aldehydes, or As illustrating the improved results to be obnitriles, is reduced to a practically negligible ed y the use Of the catalyst of y inven- 50 amount. tion, comparative tests were run under the con- 50 In the following examples I have set forth s vditions and amounts of material just stated, but eral of the preferred embodiments of my invenu in a ata yst n i n of a u num p stion, but they are presented only for purposes of Dhate instead of e p g ted, rigid gel cataillustration and not as a limitation. lyst of the invention.- At 300 0., there was ob- Example 1.-A catalyst composed of alumina tamed a conversion to amines or only 12%. while 55 the loss to butylene was 2%. At 350 0., the conversion to amines was 31%, but with a 28% loss to butylene.

Example 4.--A catalyst consisting of boric anhydride supported on silica gel was prepared by impregnating 60 grams of silica gel with 100 cc. of a 20% solution of ammonium borate in the manner described in Example 1. This catalyst when used for the synthesis of methyl amines from methanol and ammonia at a temperature of about 350 C. and a ratio of alcohol to ammonia of 1:2, and a tim of contact of 3-5 seconds gave ,yields of amines or 15% and over.

Example 5.Tri-butyl amine and ammonia in the molecular ratio of 1:6.5 were passed at 400 C. over the catalyst described in Example 1, the time of contact of gas with the catalyst being 2.6 seconds. Under these conditions, approximately 66% of the tri-butyl amine was converted to monoand dibutyl amine with a conversion to butylene of only 3%.

While I have indicated the use of certain particular catalytic components for the impregna tion of the porous, rigid gels, it is to be under= stood that my invention is not limited to their use. For instance, the finished impregnated gel may contain the oxides of such metals as tungsten and titanium, and even other oxides or mixtures of oxides which have the property of catalyzing dehydration reactions.

Furthermore, the preparation of the catalysts of the type herein described need not be limited to the particular method described above. For example, instead of previously evacuating the gel support, the gel may be soaked at atmospheric pressure, or at higher pressures, in a solution of suitable concentration of a salt of the metal selected as the catalytic component, followed by drying and ignition of the impregnated material to decompose the salt to a metal oxide. An alternative method may involve the use of a hydrous oxide, such as hydrous aluminum oxide, which may be precipitated on the gel support from a solution of its salt by means of a base such as amnionia.

Any salt, such as a nitrate or carbonate, which is capable of being decomposed by heat to the desired oxide, may be used for impregnation of the gel support.

The preferred concentration of the salt solutions used in impregnating the gel is about 20%. However, since the concentration of the solution is a relatively important factor in determining the amount of dehydrating oxide which is deposited on the gel, this may be varied between a 1% concentration and the concentration representing a saturated solution of the particular salt used.

Other porous rigid gel substances may be used in place of silica gel within the scope of the invention. For example, alumina gel or a zeolite may be used for this purpose. Furthermore, inert gel-like materials, gelatinous precipitated hydroxides or salts may also be employed.

The temperature limits between which the catalysts are operated may vary from 250 C. to 500 0., although the preferred range is from 300-3 50 C. The mol ratios of alcohol to ammonia may also vary from as low as 1:0.25 to as high as 1:10. It is also to be understood that other conditions, such as time of contact of the gas with the catalyst, may be varied widely within the scope of the invention.

It is further to be noted that the impregnated gel catalysts herein described may be used in 1"B=- actions involving the use of pressures substantially above atmospheric.

The use of the catalysts prepared as described above may be applied to various hydration or dehydration reactions, such as the production of unsaturated hydrocarbons or ethers from alcohols, the hydrolysis of ethers, such as dimethyl ether, with steam, or in the elimination of water between acids and alcohols to form esters.

These porous catalytic materials are especially valuable in the synthesis of amines from alcohols and ammonia. The use of these catalysts is, however, not confined to the synthesis of aliphatic amines from aliphatic alcohols, but can also be applied to the synthesis of aromatic amines as well. Furthermore, a secondaryor tertiary alcohol may be substituted for a normal alcohol, and an aliphatic or aromatic amine, such as aniline, may be substituted for ammonia. Catalysts of this type may also be used in the synthesis of mixed amines from mixtures of alcohols, such as methyl and butyl alcohols and ammonia.

It seems desirable at this point to discuss briefly the theory of the use of these catalytic materials, although such discussion is included merely for the purpose of more clearly describing the invention and is not intended to be in any sense a limitation thereof.

In the case of the synthesis of amines from. aliphatic alcohols higher than methanol, two dehydration reactions are possible. One involves the elimination of water between the alcohol and the amine according to the equationwhich is the desired reaction and in which n represents a whole number not greater than 3, and R represents an alkyl group. The other reaction, which is the undesired reaction, involves the elimination oi" water from the alcohol molecule itself, resulting in the formation of an unsaturated hydrocarbon according to the equation- (2) CnH(2n+1)OH" CnH(2n)+H2O in which n represents a whole number.

The particular advantage of the use of the catalysts of my invention is the fact that they promote the reaction represented by Equation (1) with the substantial repression of the reaction represented by Equation (2).

Another advantage lies in the ease and cheapmess with which a catalyst of the type described may be prepared as compared with such catalysts as basic aluminum sulphate or hydrated alumina which involve precipitation, long and tedious washing and diii'icult filtration. My improved catalysts also possess the advantage oi. high activity in'practically all dehydration reactions.

As many apparently and widely. diflerent embodiments oi this'invention may be made without departing from the spirit and scope thereof,

it is to be understood that I do not limit myselfto the specific embodiments thereof except as defined in the appended claims.

I claim:

1. The process of producing a lower aliphatic amine which consists in passing a mixture of a vaporized lower aliphatic alcohol and ammonia over a catalyst comprising essentially a. rigid, porous silica gel impregnated with aluminum oxide at a temperature of 250-500 C.

2. The process 01 producing a mixture of butyl amines, including mono-, di-, and tri-butyl amines, which consists in passing a mixture of vaporized butyl alcohol and ammonia at a temperature of 250-500 C. over a catalyst comprising essentially a rigid, porous silica gel impregvaporized butyl alcohol and ammonia at a temperature of at least 300 C. over a catalyst prepared by evacuating silica gel at about 400 C. to remove absorbed and adsorbed gases and liquids, cooling the evacuated gel under vacuum, and thereafter impregnating said gel with aluminum nitrate, and igniting the impregnated material.

5. The process of producing lower aliphatic amines which comprises passing a mixture of a vaporized lower aliphatic alcohol and ammonia over a catalyst comprising essentially a rigid, porous gel impregnated with a dehydrating oxide, at a temperature of 250-500 C.

6. The process of producing lower aliphatic amines which comprises passing a mixture of a vaporized lower aliphatic alcohol and ammonia.

over a catalyst comprising essentially a rigid, porous silica gel impregnated with a dehydrating oxide, at a temperature of 250-500 C.

7. The process of producing a mixture of butyl amines, including mono-, di-, and tri-butyl amines, which consists in passing a mixture of vaporized butyl alcohol and ammonia at a temperature of 250-500 C. over a catalyst comprising essentially a rigid, porous gel impregnated with a dehydrating oxide.

8. The process of producing a mixture of butyl amines, including mono-, di-, and tri-butyl amines, which consists in passing a mixture of vaporized butyl alcohol and ammonia at a temperature of 300-400" C. over a catalyst comprising essentially a rigid, porous gel impregnated with a dehydrating oxide.

9. The process of producing a lower aliphatic amine which comprises passing a mixture of a vaporized lower aliphatic alcohol and ammonia at a temperature of 250-500? C. over a catalyst prepared by subjecting a rigid, porous gel to a vacuum to remove absorbed and adsorbed gases and liquids, and thereafter impregnating said gel with a solution containing a material yielding on ignition a catalytic dehydrating oxide and igniting the impregnated material.

10. The process of producing a lower aliphatic amine which comprises passing a mixture of a vaporized lower aliphatic alcohol and ammonia at a temperature of 250-500 C. over a catalyst prepared by subjecting a rigid, porous silica gel to a vacuum to remove absorbed and adsorbed gases and liquids, and thereafter impregnating said silica gel with a solution containing a material yielding on ignition a catalytic dehydrating oxide and igniting the impregnated material. I

11. The process of producing a lower aliphatic amine which comprises passing a mixture 01 a vaporized lower aliphatic alcohol and ammonia at a temperature of 250-500 C. over a catalyst prepared by subjecting a rigid, porous gel to a vacuum to remove absorbed and adsorbed gases and liquids, and thereafter impregnating said gel with a solution containing an aluminum salt which will form an oxide upon ignition and igniting the impregnated material.

12. The process of producing a lower aliphatic amine which comprises passing a mixture of a vaporized lower aliphatic alcohol and ammonia at a temperature of 250-500 C. over a catalyst prepared by subjecting a rigid, porous silica gel to a vacuum to remove absorbed and adsorbed.

gases and liquids, and thereafter impregnating said silica gel with a solution containing an aluminum salt which will form an oxide upon ignition and igniting the impregnated material.

13. The process of producing an amine which consists in passing a mixtureof a vaporized lower aliphatic alcohol and a member of the group consisting of ammonia and aniline over a catalyst comprising essentially a rigid, porous gel impregnated with a dehydrating oxide, at a temperature of 250-500 C.

14. The process of producing an amine which consists in passing a mixture or a vaporized lower aliphatic alcohol and a member of the group consisting of ammonia and aniline over a catalyst comprising essentially a rigid, porous silica gel impregnated with a. dehydrating oxide, at a temperature of 250-500 C.

15. The process of producing lower aliphatic amines which comprises passing a mixture of a vaporized lower aliphatic alcohol and ammonia over a catalyst at a temperature of 250-500 C., said catalyst comprising essentially a. rigid, porous gel impregnated with a mixture of dehydrating oxides.

HERRICK R. ARNOLD. 

